Sergeant Bluff climate

Sergeant Bluff Frost Dates and Growing Season

NOAA 1991-2020 normals for Sioux City Gateway AP, 2.2 km from Sergeant Bluff, elevation 1095 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sioux City Gateway AP. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around April 29 and the first fall freeze around October 5, a growing season of about 159 days.

Median at 36°F
last May 7, first September 28
Median at 32°F
last April 29, first October 5
Median at 28°F
last April 20, first October 15

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 21May 16May 13May 10May 7May 4May 2Apr 30Apr 26
32°FMay 14May 8May 4May 1Apr 29Apr 27Apr 24Apr 21Apr 16
28°FMay 3Apr 29Apr 25Apr 23Apr 20Apr 17Apr 14Apr 11Apr 7
24°FApr 24Apr 19Apr 15Apr 13Apr 10Apr 7Apr 3Apr 1Mar 26
20°FApr 15Apr 10Apr 6Apr 2Mar 31Mar 28Mar 24Mar 20Mar 13
16°FApr 5Mar 31Mar 27Mar 24Mar 20Mar 17Mar 13Mar 10Mar 5

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 14Sep 19Sep 22Sep 25Sep 28Sep 30Oct 2Oct 5Oct 9
32°FSep 22Sep 26Sep 29Oct 2Oct 5Oct 8Oct 11Oct 14Oct 18
28°FSep 29Oct 4Oct 9Oct 13Oct 15Oct 18Oct 20Oct 23Oct 28
24°FOct 9Oct 15Oct 19Oct 22Oct 25Oct 27Oct 30Nov 2Nov 6
20°FOct 20Oct 25Oct 29Nov 1Nov 3Nov 5Nov 8Nov 11Nov 17
16°FOct 31Nov 3Nov 6Nov 9Nov 11Nov 15Nov 18Nov 23Nov 28

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F158153149145142138134130123
32°F177171166162159154150146140
28°F196190185181177173168163156
24°F218211206201197193189184176
20°F239231225220216212207202195
16°F257250243240236231226219213

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
6,860
Cooling degree days, base 65°F
866
Growing degree days, base 40°F
5,153
Growing degree days, base 45°F
4,057
Growing degree days, base 50°F
3,077
Growing degree days, base 55°F
2,215
Growing degree days, base 60°F
1,478

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,39600
February1,13401
March877124
April4907103
May19757340
June26195619
July4289750
August11219673
September12188423
October4649130
November873015
December1,26800

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 2.2 km from Sergeant Bluff. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00014943 (Sioux City Gateway AP). Public domain.